<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>效率测试</title>
</head>
<body>
    <script>
        function fn() {
            var d1 = +new Date();
    
            var str = '';
            for (var i = 0; i < 1000; i++) {
                document.body.innerHTML += '<div style="width:100px; height:2px; border:1px solid blue;"></div>';
            }
            var d2 = +new Date();
            console.log(d2 - d1);
        }
        fn();
    </script>
</body>
</html>